The ability to operate gas turbine engines at higher temperatures improves the efficiency of the engine. This higher temperature operation requires the use of high performance materials such as special steels, titanium alloys and Superalloys. In order to obtain the required material characteristics, these materials are often forged and age hardened.
Due to the high value of such components, there is a need to be able to repair them when they become damaged in service, for example due to the ingestion of debris into the engine.
One technique for the repair of such components is additive layer repair using a blown powder addition process. FIG. 1 shows a schematic illustration of such a process in which a deposition nozzle 10 is used to direct a flow of powder 20 onto a layered build surface 30. The powder may also be added off-axis to the main laser beam delivery. The deposited powder is then simultaneously melted into the weldpool using a directed laser beam 40. In this arrangement, the deposition nozzle 10 is fed with a supply of the powdered repair material 50. As the powder addition nozzle and laser moves away from the deposit area the meltpool created by the laser solidifies behind it.
It is normally desired that the repaired area of the component has mechanical properties that are at least equal to those of the original component. This in turn requires the repair process to be able to create a cast material having at least equal properties to the forged and sometimes age hardened base material.
For some materials this is known to be difficult, if not impossible, to achieve using a conventional blown powder additive layer repair technique.